|Why are whales mammals and not fish? What are the
characteristics of mammals?
Whales, dolphins, porpoises, seals, walruses,
and many other marine animals are mammals, not
fish. The marine mammals exist because about 50
to 60 millions of years ago, some mammals wandered
off of the land and into the ocean, and there they
evolved into different types of marine mammals.
For whales and dolphins, their front legs turned
into flippers. Their back legs became really
tiny, so tiny that you can't even see them when
you look at these animals, but they have hind legs
still inside their bodies -- if you see a skeleton
of a whale you can see it has tiny leg bones near
its tail. Here's an interesting discussion of the
hind legs in whales and dolphins: whales
Like mammals, whales and dolphins breathe air
through a pair of lungs, they are warm-blooded,
their young drink milk, and they have hair
(although very little). The whale is actually
the closest living relative of the hippopotamus.
Here's some good information on the difference
between whales and dolphins and fish: cetacea-mammalian-nature
Whales are mammals because they give birth to
live young, they have fur (although it is very
sparse on their body), they have lungs and breath
air and they provide milk for their young.
You have a lot of interesting questions about
marine mammals. Dolphins and other whales are all
mammals called cetaceans. Mammals, and only
mammals, have fur or hair and they feed their
babies milk. Whales all feed their babies milk.
You may be thinking that whales dont have any fur.
You are mostly right. They have fur when they
are fetuses, but lose it before they are born. A
few species have whiskers as adults and whiskers
are a type of hair.
There are certain characteristics that all
mammals have in common. Mammals all are
warm-blooded animals, they breathe air, have hair,
and moms feed their babies milk from mammary
glands. Whales actually do all of these things!
Whales are warm blooded, which means they keep a
high body temperature that does not change in the
cold water. Fish are cold-blooded, so their body
temperature changes depending on the temperature
of their environment. Whales actually breathe air
with lungs using their blowholes to breath out!
They come to the surface of the water so they can
breathe just like you and me. Fish get oxygen
directly from the water through their gills.
Whales even have a little bit of hair on their
smooth skin, usually on the top of their head.
Fish have scales. Whales even give birth to live
baby whales that will get milk from their mom for
food. Fish lay eggs, which must still grow into a
baby fish. So whales are indeed mammals and not
Whales are mammals because they share the
characteristics of other mammals (like us!). These
characteristics include being able to regulate
their own body temperature (unlike cold-blooded
animals, like lizards), growing hair and producing
milk to feed their young (who are born live, not
in eggs). Because of all of these traits, even
though whales live in the ocean and are generally
much bigger than us, just like people, they are
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